Save and Restore

Summary

A general architecture for saving and restoring stuff from application data areas to the USB drive.

Architecture

• A binary C-based org.webosinternals.saverestore service provides the ability to run a set of pre-installed scripts
• The service calls the scripts with a small set of known arguments (e.g. 'info', 'save', 'restore', etc)
• The scripts are named according to the appId of the application that owns the data
• The scripts are stored in a location that is only accessible by installing them as root (e.g. a signed app with a post-install script)
• The service does not allow the execution of scripts outside of that location
• Therefore, any script that is run by the service has been installed by a means that already had root access

Features of the service

• A method to list the current set of available scripts with info about id, name, ...
• A method to call an individual script, or the set of all scripts, with a command method
  • save
  • restore

Implementation Decisions

• Where to store the data
  • Choose /media/internal/saverestore

Situations To Persist Across

• Partial Erase
• Profile Reset (/var and /media/cryptofs are wiped, but /media/internal is retained)

Locations of Application Data

• /var/palm/data
• /media/internal/.app-storage
• /var/luna/data
• additional files in the application directory